The newly established structure of presqualene pyrophosphate coupled with the known solvolytic behavior of cyclopropylcarbinyl derivatives suggests that stereospecific cationic rearrangements are important for the enzymic conversion of presqualene pyrophosphate to squalene. We have initiated a study directed toward determining the efficiency and the stereochemistry of the required rearrangements in the absence of an enzyme. In order to alleviate synthetic difficulties without disturbing the electronic nature of the system, 1(R),3(R)-chrysanthemol has been selected as an appropriate C10 model for presqualene alcohol with which to attain two general objectives. We plan to establish the natural cascade of cationic intermediates in the pool which links 1(R),3(R)-chrysanthemol and 2,7-dimethylocta-2, 6-dien-4-01 (a solvolytic C10 analog of squalene). We will also study the stereochemistry of the overall conversion, which will include (a) the specific geometry of chrysanthemol during ionization; (b) the stereochemistry of skeletal rearrangement; and (c) the stereochemistry of nucleophilic attack at the squalene terminus of the rearrangement sequence. Experimental verification of these aspects are important if proposed cationic mechanisms are to be successfully interfaced with the established stereochemistry of squalene biosynthesis. Synthetic sequences to isomeric alcohols have been developed which allow us to enter the C10 cation pool at several key junctures in order to establish preferred rearrangement modes at that point. Optically pure compounds of known absolute configuration will be used to delineate the stereochemistry for each of the above mentioned steps. Determination of product stereochemistries will require both optical correlations and well established enzyme stereospecificity. Radiolabeling techniques will permit us to determine product stereochemistry. BIBLIOGRAPHIC REFERNCES: C. D. Poulter, O. J. Muscio, Jr., and R. J. Goodfellow, "Model Studies of Terpene Biosynthesis. Synthesis of (plus-2-(trans-2'-(2"- methylpropenyl) cyclopropyl) propan-2-o1", J. Org. Chem., 40, 139 (1975).